To what extent will you be disassembling the car? Will you be removing the engine, trans and rearend? If you're going to clean up the frame and underbody, it'll be hard with them in the way.
I'd sandblast, and whatever you don't want to get sand on should be covered with plastic sheeting attached with duct tape. So, if you're leaving the drivetrain in, mask them off really well. Cover the rest of the car too. Then, jack the car up as high as you can and support with a bunch of jack stands. I'd also lay some plastic sheeting on the ground and then slide under there and start blasting. The plastic on the ground will be more comfy for you and catch a lot of the sand to make cleanup easier afterwards. You can successfully blow out the sand afterwards to the point where it won't be falling out later. Use an air blower nozzle with an extension on it that you can slide a rubber hose on it to reach into hard to reach places to blow out. Once you get the car ready to blast, the actual blasting shouldn't take very long and the results will be cleaner than any other way. I guess you have a 79, so after the cleanup, I'd spray the bottom with PPG's black epoxy primer, since the bottom of a 79 was black. Then I'd spray it with some semi-gloss black single stage urethane paint. That's using a spray gun. I guess you have a compressor if you've considered blasting, so no reason not to use a spray gun. It would look more like a quality resto that way, being clean and detailed looking, which adds value to your car. An undercoating product is not as desirable, value-wise.
No reason to use glass beads. They are much more expensive than sand. And you don't need a polishing action. Paint doesn't stick as well to a smooth surface. The Black Diamond fine sand(30-60) would be my choice. Dupont Starblast sand is great too, but costs twice as much.
I'm not sure what you do about the front suspension, since it's better to do it without those parts installed too. The greaseable parts, like ball joints and tie rod ends should be protected. If you're not doing the frame, then cover the front suspension area to keep sand from it. If you want to do the frame, you could blast just the bottom of the body, and wire brush the frame to keep sand out of the suspension and steering area.
Wire brushing with a cup brush on a drill would be my second choice. Tedious, yes, but there's no easy way, if you're doing it yourself.
Is that dry ice blasting? I wonder why it has to be dry ice and not wet ice
. Sounds good if it works, and shouldn't hurt other parts of the car, and somebody else does it. Hard part is paying for it, I suppose
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